<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p {
            /* 1em =16px */
            font-size: 50px;
        }
    </style>
</head>

<body>
    <!-- 默认字体大小是16px -->
    <!-- 最小的字体大小12px -->
    <p>字体大小</p>
</body>

</html>